If you need to build a 'top-secret' piece of equipment in the UK, there's one place many people choose to go: defence contractor QinetiQ.

In Britain's Secret Engineers, we follow workers at this leading British company on a global journey, as they reveal a handful of their secretive projects. We meet the scientists and engineers building robots to defuse Afghanistan's deadly roadside bombs and learn how they're adapting them to help in dangerous civilian situations in the UK. We find out how British experts are using 'stealth technology' to make wind turbines less visible to radar and, with unprecedented access, we follow the engineers racing to get Chinook helicopters ready for front line service, including Afghanistan.

Britain's Secret Engineers is part of the BBC series, Voyages of Construction, looking at the technology used in large engineering projects.